Nucleus accumbens: anatomy and functions

A part of the brain responsible for activating our motivation.

It is well known that the different regions of the brain, although they need to work in coordination with the rest of the brain, tend to specialize in certain functions.

This article aims to show the importance of the functioning of the nucleus accumbens, a part of the brain that is not too well known.The nucleus accumbens, a part of the brain not well known by the majority of the population, but of great relevance for the human being due to its participation in the brain reward system and the integration of motivation and action.

Where is the nucleus accumbens?

The nucleus accumbens is a subcortical brain structure, located at the point where the caudate nucleus and putamen meet the septum. This nucleus is part of the ventral area of the striatum, being one of the most important nuclei of the brain.It is one of the nuclei that make up the basal ganglia.

The nucleus accumbens is also part of the brain reward circuit, having a great influence in integrating cognitive, motivational and motor aspects, and being one of the main nuclei that allows the will to be translated into action, allowing the realization of pleasure-seeking behaviors.

Parts of this structure

The nucleus accumbens has traditionally been divided into two sections, central zone and cortex, due to its different connections with other brain areas and its greater link to the emotional or motor.

1. Cortex (Shell)

This part of the nucleus accumbens is characterized by its high number of connections with the limbic system and the hippocampus, receiving both dopamine and serotonin and glutamate from various brain areas.

It is therefore the most emotion-related part of this structure. It also has many connections coming from the frontal, the nucleus accumbens sending the collected information to the thalamus and receiving it back to the central area of the nucleus accumbens. and receiving it back to the central area of the nucleus accumbens.

2. Central area (Core)

The central area of the nucleus accumbens has functions mainly linked to motor functions, being connected to the basal ganglia, the substantia nigra and the motor cortex. Ehis area is activated to a great extent at the moment of performing emotionally meaningful actions aimed at a specific goal. directed towards a specific goal.

Main functions

The location of this structure and the connections it maintains with different brain areas make the nucleus accumbens a structure of great importance. However, to be able to see the importance of this structure and its implications it is necessary to visualize in a more direct way in which processes it participates.

Although many of them are shared by the rest of the basal ganglia, Some of these processes in which the nucleus accumbens is particularly involved are as follows.

Emotion-motivation-action integration

One of the main functions of the nucleus accumbens is to transmit information about the subject's motivation and translate it into a motor action in order to fulfill the organism's goals. This integration comes from its connections with both the prefrontal and the basal ganglia. Thus, it allows us to perform instrumental, goal-directed behaviors.

In a sense, this function of the cerebral amygdala has to do with a very important type of memory: emotional memory. This capacity is on the borderline between mental processes linked to emotion and higher psychological processes, since on the one hand it works with emotions and on the other it influences decision-making and the creation of concepts.

2. Influences behavioral planning

The connections of the nucleus accumbens with the frontal lobe have allowed us to see how this structure is involved in ideation and planning of behavior. in the ideation and planning of behavior, being as we have said an important point of integration between the motivational aspects of behavior and the motivational aspects of behavior.as we have said, it is an important point of integration between the motivational aspects of behavior and its implementation.

3. Evaluation of the situation

The participation of this structure also takes place at the evaluative level, by integrating the emotional information with the adaptive assessment of the behavior. integrating the emotional information with the adaptive evaluation made by the frontal. In this way, a stimulus is associated with a subjective evaluation by means of a process that also has to do with emotional memory.

4. Role in addiction

The nucleus accumbens plays an important role in the addictive processThe nucleus accumbens plays an important role in the addictive process, since it is linked to the experience of reward. This brain nucleus is part of the mesolimbic pathway, forming part of the brain's reward center. Specifically, it is in this area where stimulant drugs act, producing an increase in brain dopamine levels.

5. Obtaining pleasure

Although it is not the only brain structure linked to the experience of pleasure, the nucleus accumbens is closely linked to its attainment. Different experiments have shown that although its inhibition does not eliminate the desire to obtain a reinforcer, it does produce a decrease or suppression of the behaviors necessary to obtain the object of desire. The observed data show that the involvement of the nucleus accumbens is present in addictive processes, as well as in feeding and sex..

6. Learning and memory

The above-mentioned points show that the nucleus accumbens is of great relevance in establishing the automation and learning of reward-directed behaviors. of behaviors aimed at obtaining a reward. It also participates in the habituation process.

7. Aggressiveness and risky behaviors

Hyperactivity in the nucleus accumbens can lead to aggressive behavior.. In the presence of a very high level of dopamine and other alterations that hinder behavioral inhibition, it can lead to a search for personal satisfaction without valuing the risks.

In fact, studies on people with psychopathy seem to indicate that these people have, among other alterations, a severe imbalance in the nucleus accumbens, suffering from a hyperreactivity to dopamine that could induce them to seek their own reward with indifference to the consequences for others.

Bibliographical references:

• Fernandez-Espejo, E. (2000) How does the nucleus accumbens work? Rev. Neurol. 30: 845-9.

• Kandel, E. R. (2001). Principios de Neurociencia. 1º edición. McGraw-Hill.

• Salamone, J.D.; Correa, M.; Mingote, S. & Weber, S.M. (2003). Nucleus Accumbens Dopamine and the Regulation of Effort in Food-Seeking Behavior: Implications for Studies of Natural Motivation, Psychiatry and Drug Abuse. Journal of Pharmacology and Experimental Therapeutics, 305 (1). 1-8.